Molecular ecology of North Pacific otariids: Genetic assessment of northern fur seal and Steller sea lion distributions

Using different classes of molecular markers, I conducted three independent studies to examine distributions of northern fur seals ( Callorhinus ursinus) and Steller sea lions (Eumetopias jubatus ). Molecular techniques were developed and applied to studies of population distribution, seasonal distribution, and gender distribution among sites and seasons. I used eight microsatellites to examine the genetic variability and to test for population differentiation among breeding islands across the range of the northern fur seal. Genetic variation was high, and significant differences in allele frequencies were observed over all loci and populations. However, there was little evidence of heterogeneity of allele frequencies at individual loci across populations, or in single or multilocus pairwise comparisons of populations. Estimates of FST and RST were low for all comparisons (FST ≤ 0.0043; RST ≤ 0.0373), and were not significant. Tests of isolation by distance revealed no correlation between geographic and genetic distance. Despite high levels of philopatry associated with both male and female northern fur seals, and extensive variation at the microsatellite loci, I found little evidence of genetic differentiation among breeding islands. Using mtDNA haplotypes determined from fecal samples collected non-invasively during the winter, I explored the seasonal distribution and migration patterns of Steller sea lions. I compared the observed winter haplotype composition to the known summer stock distribution and found evidence of few seasonal migrants between stocks. A mixed-stock analysis supported these findings, indicating that during winter 98.6% of the animals residing in the geographic region of the western stock originated from that stock. The results substantiate current management policies for the two sea lion stocks. Finally, using fecal samples and sex chromosome markers, I examined seasonal gender distribution, and composition, of Steller sea lions at rookery and haul-out sites. Females were the predominate gender identified from summer (72.5%) and winter (61.2%) samples. Within winter collections, the percentage of samples assigned to females at rookery and haul-out sites was similar. The results indicate that terrestrial sites may be more important for females. Seasonal movement by females among sites, at least locally, is extensive and possibly reflects changes in prey availability or environmental conditions.